High Pressure Safety Valve HVAC: Description and Operation

HIGH PRESSURE RELIEF VALVE

Description
A mechanical high pressure relief valve is used to vent refrigerant from the A/C system to protect against damage to the A/C compressor and other A/C system components, caused by condenser air flow restriction or an overcharge of refrigerant.

On the TRS-090 A/C compressor, the relief valve is located on the compressor cylinder head, which is on the rear of the compressor. On the HS-15 A/C compressor, the relief valve is located on the replaceable compressor manifold.

Operation
The high pressure relief valve vents refrigerant from the A/C system when a discharge pressure of 3445 to 4135 kPa (500 to 600 psi) or above is reached. The relief valve closes when a minimum discharge pressure of 2756 kPa (400 psi) is reached.

The high pressure relief valve vents only enough refrigerant to reduce the system pressure, and then re-seats itself. The majority of the refrigerant is conserved in the A/C system. If the relief valve vents refrigerant, it does not necessarily mean that the valve is faulty.

The high pressure relief valve is a factory-calibrated unit. The relief valve cannot be adjusted or repaired, and must not be removed or otherwise disturbed. On the TRS-090 A/C compressor, the relief valve is serviced only as a part of the compressor assembly. On the HS-15 A/C compressor, the relief valve is serviced as a part of the compressor manifold.